Pen cap



FIG. 1 is a perspective view of a pen cap showing my new design;

FIG. 2 is a front elevational view;

FIG. 3 is a rear elevational view;

FIG. 4 is a right end elevational view;

FIG. 5 is a left end elevational view;

FIG. 6 is a top plan view; and

FIG. 7 is a bottom plan view thereof. 

The ornamental design for a pen cap, as shown and described. 